This week Welding Talk introduces you to welding dissimilar materials. Whether it’s mild steel to stainless, or ferrous to non-ferrous metal, dissimilar material welding challenges amateurs and pros alike. We hope our introduction provides a useful first step to demystifying this topic…
As ever when planning any welding, welding dissimilar materials begins with understanding the materials involved – such as ferrous to non-ferrous, specialised tool-steel to stainless steel or mild steel to copper. Next, consider the desired welding result, where you are going to be welding and the process available. Last, but not least, you need to consider the required consumables and material preparation. Ignore any of these with dissimilar materials and you risk work-ability problems, poor bonding and potentially disastrous effects such as cracking or even component failure....
Which dissimilar materials are you welding?
First, think about the materials you’re planning to weld. You’ll probably know what these are. However, if not, seek advice (or get a material analysis) – in particular, we’re thinking special alloys with unusual chemical compositions here.
While preparing this week’s article, the team highlighted cracking risks when welding mild steel and stainless steel. The big takeaway is that when you are welding two different metals, pitfalls await around every corner; if in doubt (or for a second opinion) please ask us for advice. With around 170 years’ combined welding experience in the team, there’s not much we haven’t come across.
Brazing vs. welding
At this point, you may realise that welding isn’t the right process for your needs. As discussed in a previous post, materials such as specialised boron steels and joining different ferrous and non-ferrous metals (such as mild steel and copper) may better-suit MIG or TIG brazing.
What result do you want?
When welding different metals together, the desired result will help you choose your approach. If high performance in a challenging engineering application is critical, you’ll go one way. Alternatively, attractive artistic finishes that don’t require high strength may lead in another direction. For instance, imagine the very different requirements of TIG-welded artwork, welding mild-steel plates to high-precision tooled-steel threads, or repairing excavator bucket-teeth in quarrying. All three environments could involve welding dissimilar metals.
Which welding process?
As usual, think carefully about your materials and the available process. Having chosen between electric brazing and electric arc welding, your approach will be similar to any welding with that process. This includes, of course, welding with the ‘stick’ side of your TIG machine if appropriate.
Choice of process typically comes down to the available machine and where you are. Are you production welding in a controlled workshop environment? That’ll probably be MIG or TIG. Alternatively, a ‘quick and dirty’ machinery repair on the most inaccessible corner of a farm will lend itself to good old stick welding.
In every case, correctly selecting the best wire or filler rod will be a key determinant of success or failure. If in doubt, please contact us – it’s what we’re here for.
Consumables for welding dissimilar metals
The subject of welding rods brings us to the important topic of consumables such as TIG and MIG filler rod and wire. Our experience reveals that when stainless steel is involved in dissimilar-material welds, 312 nickel-chromium rods, 309LSI MIG wire and 309LP rutile flux-cored MIG wire are widely used.
While you may get away with using standard rod or wire to weld dissimilar steels (or other metals), specialised rods designed for the purpose make life much easier: welds will flow nicely, penetration is optimised and metal-to-metal bonding will be better.
Of course, context is important when you are joining dissimilar materials. Our operations manager Daz Higgs highlights filler-rod choice when welding hardened steel bucket teeth to the leading edge of mild-steel excavator buckets:
‘When welding dissimilar materials, it’s essential to choose the right consumables, depending on the priority of hardness or ductility. In the mobile plant example, hardness was prioritised. What’s more, the thickness of the weld demanded stick welding with a suitable hard-facing rod. Along with good material awareness and prep, the correct rod or wire makes a huge difference to your result. We’ll help you choose from the sometimes-bewildering range available from trusted sources such as Hilco and Sif.’
At risk of sounding like that proverbial stuck record, we’d be lax not to mention preparation yet again. From experience, whether you’re welding similar or dissimilar metals, a common denominator of successful welds is thorough material preparation. Without this, even the best welding machine and consumables won’t get a fair chance. Cleanliness and dryness are vital. And while we’re on preparation, please remember the possible need to preheat your material (for instance, cast iron) – if in doubt, pre-heat for the higher temperature material.
Professional advice always helps
As with all welding and brazing, the basics of welding dissimilar materials are easy to understand. But mastery takes years of training, knowledge transfer, experience and practice.
Whether you’re welding different materials for the first time in your home workshop, or joining specialised superalloys in a high-tech production environment, we can help.
Any questions? Speak with an expert
Send us an email or call us sometime!